Printing telegraph system



o '10, 1 5 1. .DURKEE 2,658,943

' Pamzm TELEGRAPH SYSTEM I Original Filed Jan. 23, 1950 s Sheets-Sheet 1I INVENTOR. Ame/a 3) Dwqfiew, BY

A TI'ORIVFY Nov. 10, 1953 J. D. DURKEE 2,658,943

PRINTING TELEGRAPH SYSTEM Original Filed Jan. 23, 1950 3 Sheets-Sheet 2I //4g //5.9 "'6 i H /4/ 496 I .51 E. 5 d? F mmvron.

BY 6. DA/.140

TE. 1 U

Nov. 10, 1953 J. D. DURKEE PRINTING TELEGRAPH SYSTEM 3 Sheets-Sheet I5Original Filed Jan. 23 1950 Patented Nov. 10, 1953 UNITED STATES PATENTOFFICE PRINTING TELEGRAPH SYSTEM James D. Durkee, Fairlington, Va.,assignor, by

direct and mesne assignments, to Dualex Corporation, a corporation ofDelaware 14 Claims. 1

My invention relates broadly to printing telegraph systems and moreparticularly to a high speed polarized system of printing telegraphyutilizing printing telegraph apparatus of compact size and light weight.

This application is a division of my application Serial Number 139,977,filed January 23, 1950, now U. S. Patent No. 2,613,267, dated October 7,1952, for Printing Telegraph System.

One of the objects of my invention is to provide a printing telegraphsystem constituting an improvement upon conventional sequentiallyoperated systems, overcoming inherent difiiculties in these systems andto supplement the purpose for which the system described in myco-pending application No. 109,648, filed August 11, 1949, for PrintingTelegraph System was developed.

My co-pending application is directed to a printing telegraph system,which when applied to space radio systems, overcomes conditions offading, interference, and static, and is particularly adaptable tomobile radio printer operations where compactness and portability and aminimum of mechanical equipment with incidental maintenance are majorrequirements.

The system of my invention employs a polarized electrical matrix whichrequires the transmission of only five polarized pulses, without thenecessity of transmitting start-stop or synchronizing pulses, toaccomplish the thirty-two different permutations and combinations ofsignal impulses presently used in printing telegraph systems.

Since in my application a smaller number of permutations andcombinations of signal pulses are required to produce the same number ofpermutations and combinations as used in currently existing systems, agreater number of permutations and combinations can be sent in less timewith fewer impulses thereby requiring a smaller number of transmissionbands and less frequency band-width.

In addition, since the system of my invention requires only a reversalof current direction or polarity, the transition from one polarity orphase to the opposite polarity or phase may be accomplished bysinusoidal wave form; thus, the impact excitation resulting from a rapidmake or break keying operation 01' from a rapid frequency shift iseliminated, thereby further decreasing the keying band-width required atany speed of transcission.

A further object of my invention is to provide a self-synchronizingreceiving system which may be made operable over a fairly wide range oftransmission speeds and which requires a minimum of equipment oradjustment.

Another object of my invention is to provide means for supplying a pulseor pulses which may have been lost in transmission or obliterated byinterference and means for indicating on the receiving copy a mark orsymbol which visually indicates that the character received isincorrect.

The apparatus described in this application is intended for use with theprinting mechanism of my co-pending application No. 109,648 supra butmay be used with an electric typewriter or with slight modification ofthe present printing telegraph systems may be used interchangeably withconventional equipment.

My invention will be more fully understood from the specificationshereinafter following by reference to the accompanying drawings in whichFigure 1 diagrammatically shows the transmission system of my invention;Fig. 2 is a schematic plan view of a fragmentary portion of thetransmission keyboard Fig. 3 is a schematic end elevational view of thetransmission keyboard, the view being taken on sectional line 3-3 ofFig. 2 and showing the frame structure in vertical section; Fig. 4 showsthe receiving circuit of the printing telegraph system of my invention;Figs. 5 and 6 are detail views illustrating the operation of the controlmechanism in the receiving apparatus; Figs. 7 and 8 are detailed viewsof the operating solenoids controlled by the printing telegraphreceiving system; Figs. 9 and 10 are enlarged schematic views showingthe operation of the error indicating means employed in the receivingsystem of my invention, the views being shown in front elevation andwherein Fig. 9 shows the error indicating means in printing positionwhereas Fig. 10 shows the error indicating means released and free ofprinting position; and Fig. 11 is an end view of the error indicatingmeans shown in Fig. 9.

Almost from the beginning of the art of printing telegraph systemsefiorts have been made to accomplish the selection of characters byelectrical resolution of the units of the Baudot code. Each solutionrequired the use of a large number of electrical contacts andelectro-magnetic relays in simultaneous operation with the resultingpresence of a multiplicity of potential error producing elements.Practical experience indicated that greater reliability could be placedon mechanical resolution and the present state of the art reflects thisexperience. Mechanical operations, however, have the inherentcharacteristic of requiring a longer time to perform the same functionsthan does electrical energy.

However, operational communication require ments for increased speeds ofoperation have now exceeded the capabilities of the mechanical equipmentexcept under strained and abnormal conditions which require excessivemaintenance and mechanical tolerances and precision of ap paratus whichare difiicult to achieve.

The application of printing telegraph systems to radio communicationalso introduced additional dificulties which do not readily lendthemselves to solution by mechanical methods due to the speedlimitations of mechanical operations.

Two of the major difficulties introduced by radio communication arevarious forms of fading and interference in addition to the,- basiclimitation in the number of cycles available in the total radiofrequency spectrum.

Heretofore, various approaches to the radio applications of printersystems have been by increasing power of transmission and improvingreceiving conditions in an effort to duplicate the operating reliabilityof a land line to overcome fading and increasing the dot cycles ofoperation by additional fail safe impulses or increasing the units ofthe basic five unit code to provide error detection resulting frominterference and certain forms of fading.

The approach of my invention to the solution of the requirement forincreased speeds has been to eliminate the basic mechanical limitationof the mechanism used to resolve the units of the five unit code intocharacters by use of a polarized electrical matrix; to decrease theelectrical contacts required to a minimum by use of rectifying apparatusand the application of new and novel electrical circuitsand to decreasethe operational functions to a minimum by simplification of equipmentand electrical circuits.

The fading and interference problems introduced by radio communicationhave been accepted as natural characteristics of the medium. Circuitsand operations are provided. by my invention which take these naturalcharacteristics into account and provide substitute characteristics inthe form of locally produced impulses to replace those lost intransmission due to fading or to counter balance impulses introduced intransmission as av result of interference and to indicate on thereceiving equipment when these functions have been. required to completethe formation of a character.

In endeavoring to achieve greater economy of bandwidth, the start-stopor synchronizing impulses heretofore usedin both, radio and wire methodshave been eliminated in. my invention by self-synchronizing apparatusresulting in an approximate saving of twenty per cent of bandwithrequired to perform the functions necessary to the formation of acharacter as compared to systems which transmit start-stop impulses orsynchronizing impulses.

My invention employs. apparatus and methods which are compatible withexisting methods and apparatus, allowing in almost every instance, theuse, with slight modification, of existing equipment and methods toaccomplish its purpose.

Transmitting apparatus Figs. 1', 2 and 3 show the transmission system ofmy invention, the transmitting keyboard being shown in plan view in Fig.2 and inend view in Fi 3.

When the key I, pivotally mounted at la, is depressed, bars 2, 3, 4, 5and: It which extend therefrom depress levers I, 8, 9-, I0 and II in adownward direction to form. contact with. the contacts 12 to 2 I. Thelevers 'I-I,lv are supported at opposite ends in frame N6 of thetransmitting keyboard as shown at la and w; 811 and 8b; 9a and 9b; Illaand 19b; and Ha and [lb through resilient self restoring flexing stripmembers la'l'b; 8a'-8b; 3a'-5b'; iila--i0b; and l ia'l ib'. Contactsl22i are insulatingly supported in relation to frame M6 in alignmentwith thepivoted levers 'I-i i as shown. The levers 7-4 I are normallybiased by the resilient self restoring flexing strip members Yer-lb;8a'--8b'; 9a-'-9b; leer-46b; and Ha'iib, to a position in horizontalplanes and flex under the pressurev ofthe bars 2-5 in either a clockwiseor a counterclockwise direction depending on the relative positions ofthe bars 26 with respect to the centers of levers l-l I, for effectingmomentary contact at l2--2I. When pressure of bars 26 on the levers 'i-His removed the levers l-H are restored to horizontal position breakingthe contacts l2-2i by the self restoring action of the flexing supportsat each end of the levers !'-i l. The contacts which are formed dependuponwhich side of the center of levers 'lto I l, the bars- 2 to, 6 arepositioned. In the position illustrated in Fig. 1 lever 7 will contactl2, lever B will contact l5, lever 9 will contact 16, lever [0 willcontact l9, and lever II will contact 20, placing alternatively positiveand negative currents from source of battery 29 on stepping relaycontacts 22, 23, 24, and 26 arranged in the path of switch arm 2! ofcontinuously cycling driven steppingrelay 28.

When this contact was made a positive current flow took place frombattery 29 (Fig. 1) contact through I2, and the contact carried by leverl to stepping relay contact 22 through arm 21 through relay coil 38 tothe center tap 29a of battery 29. The current in coil 30 caused armature31 to move down, making contact with contact 32 which in turn caused thearmature 33 of stepping relay '28- to be moved down because of thecurrent in relay coil 34 produced by closing or" contact 32. Themovement of armature 33 caused ratchet arm 35 to pull arm 21 away fromcontact 22 counterclockwise towards stepping relay contact 23. Duringthe time the arm 2'! was in contact with contact 22, a positive voltagewas applied to line 35 with respect to ground or center tap 29a ofbattery 29, or was caused to flow through rectifier '38 through relaycoil 38a in a positive direction re sulting in movement of arm 39 ofrelay 40 to make contact at 43 which in turn keyed the marking frequencyof a frequency shift radio printer keying circuit.

As soon as arm 27 left contact 22' the current in relay coil 3%] wasreleased and contacts 3! and 32 were opened de-energizing coil 34 of thecontinuously cycling spring driven stepping relay 28 which in turnrepositioned ratchet arm 35 preparatory for another ratchetingoperation.

The capacity 4| and adjustable resistor 42 across coil 34 acts to retardthe arm 21, suiiiciently long at each contact 22 to 25 to permit thefull cycle of operation previously described to be completed.

When arm 2? arrived at contact 23' the same cycle of operation was setin motion as when the arm 21 was at contact 22, except that the chargeof voltage on contact 23 is now derived from the negative source ofbattery 29, thru the contact on lever 8 and contact [-5- and a negativecharge was placed, thru rectifier 3"! and relay coil 31a to ground orcenter tap 29a of battery 29, causing armature 39 to close contacts 44keying the spacing frequency of the frequency shift keying system orcausing a negative charge to be placed on line 36.

The same cycle of operation is repeated at stepping relay contacts 24,25 and 26 resulting in moving arm 21 back to the original position incontact with contact 22 having thus completed a transmission cycle offour self-cycling operations from contact 22 to contact 28 which vresulted in sending four equally spaced pulses and one starting pulse ofalternate positive and negative charges to a line or causing the twofrequencies of a frequency shift keying system to be alternativelyoperated causing five pulses divided between two diiferent alternatingcurrents to be transmitted.

Since the pulse caused to be transmitted when arm 21 is in contact withcontact 22, is the starting pulse, it does not have to be especiallyspaced in relation to any previous pulse. The pulse created by contactof arm 21 with contact 28 is the end of the character formingcombination.

Figs. 2 and 3 show the arrangement of the transmission keyboard moreclearly from which the coaction of the pivoted keylevers 45 with thecontact control means will be understood. The key-levers are arrangedabove the angularly shiftable levers 1, 8, 9, I8 and II and through bars2, 3, 4, 5 and 6 selectively control the angular movement of the leversabout their pivots 1a, 1b||a, III), that in turn control the contactsI2, I3, I4, I5, I6, I1, I8, I9, 28 and 2|, for controlling the circuitsheretofore described.

When arm 21 arrives at contact 28, current from negative battery 29flows through coil 46, arm 21 and coil 38 to the center tap 29a ofbattery 29. This causes armature 41 to be attracted by theelectro-magnetic core of coil 46 making contact at 48, permittingcurrent to flow through coil 49 from positive battery 29 to negativebattery 29. When coil 49 shown more clearly in Fig. 3 was energizedarmature 58 was drawn towards the electro-magnetic core of the coil 49pushing oscillating bar 58 against armature 5| releasing pressure ofpoint 5Ia of pivoted member 5| on roller 52 carried by the end ofkeylever 45 permitting spring 53 to pull keylever 45 up against stop 54which action lifted key bars 2, 3, 4, 5 and 6 from bars 1, 8, 9, I8 andII, allowing the latter to resume normal position. Thus permutations andcombinations of signal pulses can be formed and transmitted by contacts43 and 44 under selective control of the keyboard as described.

Had it been desired to utilize the keying mechanism in the mannerdescribed in my co-pende ing application No: 109,648 supra forsimultaneous transmission of a coded character, the oscillators 48a,48b, 40c, 48d and 48c of the circuit of Fig. 1 of that application wouldbe connected to contacts I3, I5, I1, I9 and 2|, and levers 1, 8, 9, I8and II would be connected together and returned to contact with 48Contacts I3, I5, I1, I9 and 2| would have been disconnected and levers1, 8, 9, I8 and II, when in normal position, would have been makingcontact with contacts I2, I4, I6, I8 and 28 causing oscillators 48a,48b, 48c, 48d and 486 to continuously generate alternating current tonesinto the line 36 or an amplifier as described in my aforesaid co-pendingapplication. When key is depressed contact is broken at contacts 1, I2,at 9, I4 and at |I,28, causing oscillators 48a, 48c and 48e to beremoved, from 6 the line and the character which is made up of signalsfrom oscillators 48b and 48d in simultaneous combination would beformed.

Receiving apparatus Fig. 4 shows the receiving circuit for the receivingprinter of my invention. I provide a pyramid or Christmas treearrangement of relays 63, 91, I83, and H8, in series with a rectifiercircuit, and having associated armatures 18, 98, I84, and III,respectively, arranged to control permutations and combinations ofsignal pulses through associated contacts and circuits connectedtherewith. An unlatching or fifth relay H8 is used for controlling anarmature II1 for unlatching armatures 18, 98, I84 and III for enablingthe system to receive the next succeeding signal impulse group. Thepermutation and combination incoming signal pulses, whether received byline or as a result of rectification of a radio or audio frequencycurrent, appears on line I41 of Fig. 4 as a positive or negative voltagewith respect to ground.

55 in accordance with the manner in which it was transmitted by theapparatus described in Figs. 1-3. The current flows through the steppingarm 8| of cycling switch 82 to contact 56 and the winding of relay 63and, if the voltage is orpositive polarity with respect to 55, which isthe center tap 29a of battery 29 from which the voltage on line I41 isderived, through rectifier 84 to line 55. The current also flows throughcoil 95 from line I41 to line 55.

When current passed through coil 85, armature 88 made connection withcontact 81 completing the circuit between positive battery 29 and coil88 and ground 55. This moved armature 89 to the left causing ratchet arm18 to turn ratchet wheel 1|, which caused arm 8| to move from contact 58to contact 51, and through shaft I45 caused arm 12 to move from opencontact 13 to contact 14.

When armature 88 moves to the left under control of coil 65, armature 98makes connection with contact 61. An extension rod 96a interconnectsarmature 88 with the operating spring 691) and draws operating spring981) to the left whereby the continuity of the circuit I41 to arm 8| isbroken between spring 882) and spring 880, insuring against thepossibility of a prolonged pulse causing a false operation prior to thecompletion of the pulse duty cycle. This also permits the carrier orsignal current to be maintained in an on condition during the interimbetween the formation of signal characters.

When current is passed through relay 69, armature 18 causes extensionbar 19 to pull contacts 88 to 81 into connection with contacts 89, 98,9|, 92, 93, 94, 95 and 96.

Upon arrival of arm 9| at contact 51 the circuit from line I41 throughrectifier 84 to line 55 is completed. If the voltage on line I41 is nownegative, rectifier 84 will not pass current through relay coil 91 toground 55 and thus armature 98 remains in position shown and contacts toI82 are not broken.

The current, through coil again causes the arm 6|, as a result of theaction similar to that previously described, to move to contact 58. Ifthe voltage in line I41 is now positive with respect to ground or centertap 29a of battery 29 and the circuit is completed from line 41 througharm 8|, contact 58, coil I83, to rectifier 84, and. line 55, the currentflow through coil I83, causes armature I84 to move bar I 85 causing leafspring contacts we and. lit! to conn ct with con acts 508."

the circuit from line; I412 through coil 1.10,. arm: 62I1: contact 59,.to rectifier 64; the, noltage: is.

nownegative, rectifier M will. not pass current; through coil. iifltoground fiiaand armature: MI.- and bar 1 i2 remainin the. positionshown The. current. in. coil. 6 5 present. when. contact. 62 of arm tiis. in contact-:with. contact 5.9; causes arm BI tomovetQcOntact-EIIandarmH to more. to. contact TI:

I41 is now-connected thrir arm.6.I contact. 60? and contacts: H3; I Eil-IaGEh. "It, 85 and. 9%,-

to. the printer magnets N. and SE; to. rectifiersv Hat and :5 to line 55through: lea-($5511.

If: the voltage. in. line 11th was positive: when contact: was made by.arm 51: atcontactrfifi; aposie tive. current. will. now pass through theprinter. magnets N? (Fig. 4) and rectifier I115; to. and by. the processdescribed above.. the letter N of the printer tQprint.

When the letter N functionwas; activated by the action of arm GI;contacting contact 6.51; cur.- rent also passed through relay; coil:161111117116? lead' 55a which caused armature H112 to. unlatch armatures18', 94",. I184: and: MI of? relays: 9?, I03 and H preparing: thesystemmo: receive a. new cycle oficharacter forming. impulses.

Examination of Fig. 4.Wi1llSh0Wrth8;-l7,. predicatedupon the polarity ofcurrents. in line: Mi'with; respect to line55: aspresented to the:pyramid? or Christmas. tree shown; in. the lower right hand portion ofFig. 4- insequentiali. combination and with the use of pressure rollersprings H181, I19; I26 and IN to latch armature; 1.8;. 9%, Iiii and IIIin a fixed position for a periodcoverin the cycle of operation; itis-possible toindividually select any one of the multiplicity ofmagnets. in various permutations. and. combinations repre sented byreference Let? designating: letters? to -B1k designating blankf of. Fig;4; In: Figs. Sand 6 I 'haveshown the twolimiting positions of armature IH. on an, enlarged scale toillustrate the two extreme latchedpositionsthereof:under. control of pressure roller spring: H82. All; of:the. armatures: T8 98, I84- are. arranged in a. manner; similar toarmature. i:I.:I;, thatisthe armature 1.8; $181 and Hit arecontrolledjin. their limiting posi'e tions by pressure rollersprings:1.21; lid and; Iii respectively.

Figs. 7 and 8 are enlarged: views. of: the: sole;- noids in thepolarized pyramid or Christmas: tree" circuit wherein Fig.'lz'represents the juxtae positions of the differentially: polarized;operating solenoids for letters W'and'Av and letters-Z and E'- whileFig. 8 shows: the. electricaliequivalem oi the same juxtapositionedsoienoidsl The capacitor-resistor combination. I12: and I23, are usedtocontrol: the dissipationofi'current in condenser I22 through-coilfidzaiter opening of the circuit to battery 29. (1+). by'the operationof'relay: 65 and which in turn controls;the length of time which arm 61*moves" from one contact to the other of'the-group of" contacts 5.6 toBil Under certain conditions of operation: particularly in radiocircuits the possibility of lossof one or more impulses due to fadingor-obliterae tion of signals by interference is' always present.

will cause.

8. Tc overcome this condition provision has been. made in the selectorsystem for. the. supplying. of lost impu ses; andz recording thiscircumstance. on; the-printed copy; The effect of interference isimadetoappear asza lost impulse in this system.

. energy storedin capacitor 21 starts-discharging through resistors I28and lite-into coil I-29-hold.- ing; armature. m5.- that; is in, circuitwith condenser I30 through: contact I26. to battery 29.

If. no roltagerappears. on; line I417!- for a: fixed:

miod ofitimeafter contact-has been established. bwarmti with anyone ofthe contacts. 5?, 58-, 5B and; id-"before the dissipation ofenergy inCD11:'- denser I2! is complete, armature I will be released fromcontact. [26. and contact will be establishemwith; contact I31 allowingcondenser liflzto; dischargethrou hresistor I-a-, coil. 132, am I2.and;c0ntact:l4,.15; It or. ll: of: a duplicate bank; of: contactsonthe:same; shaft as contact arm: Eli to: line.- H.453 through: whichever;circuit arm 6.1% provides through its contact withrcontacts;v 55 to611:, thus; producing; the same; action. which; would; have resulted.from; an. incoming Si nal, on, line:- I451.

When. this. cnrrentrpassedi through coil I32: the.

armature. I%33;- was. moved; and. closed. the; circuit through contacttfimconnecting battery- 29; to a relay 1:31; associated; with theprinting mecha- Wheir the; relay I34; was. energized; the armature I35wasattracted. to;the. ole of coil I34-, latching itself to; latching.armature. I36 and. bringingthezextension wire I31 of armature. I35.-acrossthesurface of the character Afor; example. on the type pallet.Ifitwhich may strikethe. ink.

is ribbon- Hit of Figil; andbeprintedonthe; paper.

web I40 being advanced. on. platen. MI 01: the: printer as shown more:clearlyirr Rigs. 9. and; 10', and: 1 1. Fig; 9showsthecondition.for-indicating. error'whileFig; lO-showsanaall clearcondition with the errorindicatorremoved.

When relay I I'G- was energized contact was: made between I44 and Ifill;placing: battery. on. coil: M2 which caused armature: I36 to releasearmature I 35 allowing spring I53 to draw'armacture I35- to-itsnormalposition-.with the. extensi'om I'3liclear of the printingsuriace oftheenext character placed in. a. printing; position.

When the letter key is operatech tozprint the; character'f-ormed; partlyby. the self-imposed. impulses of condenser M9,. the character; which;is printed willbo marked by a: verticalbar stroke bythe extension barI31 of armature-I35 plainly: indicating to: the: operator thatthe.'cha1:acter wasnotiproperlyreceived;

The rotary selecting printing mechanism: dc..- scribedin my-co-pendingapplication No;.109.;648 supra may be used in connection with theapparatus described in this application to select and print thecharacters and perform the other Operations required ofa printingmechanism; This may; be accomplished by connecting the contacts. of:the. rotary switchand the; letters, figures-""and space. relays to. thecontacts. rep.- resented by. thezsolenoids for-letters K,. etc. of?"Fig. 4r

It will be fully understood that these same contacts of Fig. 4 can beconnected to a series of solenoids or magnets and be used to operate anelectric typewriter or initiate the Printing mechanism of other types ofpresently used printing telegraph equipment.

Conventional printer mechanism is operated by the solenoids lettersthrough blank shown in the polarized pyramid or Christmas tree in thelower left corner of Fig. 4.

Due to the fact that the necessity for a mechanical selector iseliminated in the printer system of my invention and yet very accurateand quick movement of theseleotion system of my invention obtained byuse of positive and negative electrical impulses, I am able to reducethe size and weight of the equipment, as compared to conventionalequipment, very materially.

While I have described my invention in cer-,

tain of its preferred embodiments I realize that modifications may bemade and I desire that it be understood that no limitations upon myinvention areintended other than may be imposed by the scope of theappended claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is as follows:

1. In a printing telegraph system, a plurality of pairs of printeroperating solenoids each including differentially polarized individualsolenoids, a polarized pyramid circuit, selective conditioning means forcontrolling said polarized pyramid circuit for selectively exciting theindividual printer solenoids of said pairs of printer operatingsolenoids by positive or negative current pulses, a signal inputcircuit, a stepping switch including an arm operative over amultiplicity of contactors, control relays individual to the saidcontactors, and means in said signal input circuit for selectivelyoperating said stepping switch relative to signal pulses for selectivelyexciting certain of said relays, and means operated by said relays forcontrolling said polarized pyramid circuit.

2. In a printing telegraph system, a circuit for receiving positive andnegative signal current pulses, a step-by-step switch controlled by saidpulses, contactors individual to the step-by-step positions of saidswitch, relays selectively excited by currents from circuits extendingfrom said contactors, a polarized pyramid circuit including sets of makeand break movable contactors with associated contacts, means operated bysaid relays for controlling the displacement of said make and breakmovable contactors with respect to the associated contacts, anddifferentially polarized printer solenoids arranged in pairs andconnected with the contacts in said polarized pyramid circuit andselectively operative by positive and negative current pulses forselectively operating printer mechanism.

3. A printing telegraph system as set forth in claim 2 including meansfor latching said movable contactors in selectively displaced positions.

4. A printing telegraph system as set forth in claim 2, including meansfor simultaneously restoring said movable contactors in said polarizedpyramid circuit to the original positions thereof from their displacedpositions.

5. A printing telegraph system as set forth in claim 2 in which saiddifferentially polarized printer solenoids are selectively connectedthrough unidirectional current feed circuits whereby the individualsolenoids of each pair are 10 selectively excitable by current pulsesaccording to the polarity thereof.

6. A printing telegraph system as set forth in claim 2 which alsoincludes an auxiliary circuit selectively excitable under conditions offailure of receipt of all of the current pulses constituting a signalpermutation or combination.

'7. A printing telegraph system as set forth in claim 2 which alsoincludes an auxiliary circuit operative upon failure of any one of thesignal permutations or combinations and means for restoring saidauxiliary circuit to normal condition after correction of the failedpermutation or combination.

-8. A printing telegraph system as set forth in claim 2 which includes acircuit containing an electrostatic capacity wherein said electrostaticcapacity accumulates an electrical charge upon the incomplete receipt ofa code signal permutation or combination, an electrical circuitcontrolled by said electrostatic capacity, a relay controlled by saidelectrical circuit, and means for restoring said relay to normalcondition after dissipation of the electrostatic charge in saidelectrostatic capacity.

9. A printing telegraph system as set forth in claim 2 in which saiddifferentially polarized printer solenoids are arranged in pairs by aconnection bonding adjacent ends of the windings of said solenoids andwherein the opposite ends of each winding are connected in series withseparate rectifiers which are polarized to pass current through one ofsaid solenoids in one direction and to pass current through the othersolenoid in the opposite direction.

10. A printing telegraph system as set forth in claim 1 in whichunidirectionally current conducting devices are electrically connectedin series with the individual solenoids of each of said pairs of printeroperating solenoids for selectively supplying operating current to saidprinter operating solenoids unilaterally according to the operation ofsaid polarized pyramid circuit. v

11. A printing telegraph system as set forth in claim 1 in which thereare at least four of said control relays each having an operatingarmature for controlling the operation of said polarized pyramid circuitand wherein a fifth relay is connected in series with said polarizedpyramid circuit and is provided with an armature onerative after eachprinting operation to restore the armatures of the aforesaid controlrelays to positions preparatory for receiving signal impulsesrepresenting a succeeding character.

12. A printing telegraph system as set forth in claim 1 in which thereare at least four of said control relays each having an operatingarmature for controlling the operation of said polarized pyramidcircuit, the windings of said control relays all being connected withsaid signal input circuit through a rectifier for sup-plyingunidirectional operating pulses to said windings and wherein a fifthrelay is connected in series with said polarized pyramid circuit and isprovided with an armature aligned with respect to all of the armaturesof said control relays and operative after each printing operation torestore all of the aforesaid armatures to positions preparatory forreceiving signal impulses representing a succeeding character.

13. A printing telegraph system as set forth in claim 1 in which themeans in said signal input circuit for selectively operating saidstepping 11 7 switch comprise a pair of relays, due a! said relayshaving its winding 'Veenneeted in said si nal input eircuit andoperating an armature-101' controlling a multiplicity'of leaf sprin sand assooiated contacts; the other pf said relays having its windingconneetedin series with one of the aforesaid leaf springs and associatedcontacts and having an armature ,ratchetmg the arm of said steppingswitch, certain of the leaf springs and contacts of said aforementionedrelay forming a circuit path ior signal impulses through said steppingswitch and one of the leaf springs and associated contacts Roi theaforementioned relay forming a circuit path through said last mentionedrelay ior ,efiecting a stepping Qperation of said steppingswitchaccording to the .re- .ception of the vsignal pulses and a rectifierdisposed in circuit with saiderm for restricting the current flowtherethrough to unidirectional pulses.

.14. A printing telegraph system as setiorthoin claim ,1 in which threeindependent reetifiers are 12 disposed in the cireiiit of said telegraphsystem (one of said rectifiers being connected .in serieshetweenlsaidisignail input veinmit and said control relays and the ether'01 said rectifiers being connected in series with said solenoids .insaid pyramid circuit, said last mentioned rectifiers being electricallyreversed with respect to each ether whereby current flows.unidirectionally in 1 said pyramid \circuit in opposite directionsaecording to the permutations and combinations of the signal pulses.

JAMES TD. DURKEE.

References Cited in "the me of this "patent

